Nerve growth factors (which will hereinafter be abbreviated as "NGF"s), many of which exist primarily in the hippocampus and cerebral cortex, are neurotrophic factors which stimulate differentiation or growth of neurocytes and are therefore essential for maintenance of function and survival. They act on catecholamine activating neurons in the peripheral nervous system, as well as on cholinergic neurons in the brain. Alzheimer's disease is thought to have, as its main lesion, degeneration and defluxion of cholinergic neurons. Therefore there has been an attempt to administer NGFs into the brain for the treatment of Alzheimer's disease. NGFs, however, cannot pass through the blood-brain barrier because they are proteins having molecular weights as high as 12,000. Therefore such treatment has not proven practical as a therepeutic method for humans. If there existed a low-molecular-weight compound which exhibited NGF-like effects and could pass through the blood-brain barrier or a compound capable of enhancing NGF synthesis in the brain, such a compound would likely be therapeutically useful for treating Alzheimer's disease. Based on this idea, substances exhibiting NGF-like effects have been sought. As a result, it has been shown that long-chain alcohols such as n-hexacosanol induce in vitro production of NGFs in gliacytes, thereby promoting neurite growth. In addition they can pass through the blood-brain barrier in vivo (Japanese Patent Application Laid-Open No. HEI 4-502167).
Effects of n-hexacosanol, however, have not been satisfactory yet.
An object of the present invention is therefore to provide a medicament comprising a compound which can be orally administered, which readily transfers into the brain, and which permits neurite growth in the brain even at low concentrations compared with those of the above-described long-chain alcohols such as n-hexacosanol.